The present invention relates to a multi-port valve, and in particular, to a multi-port valve that prevents the blockage of flow through a pre-selected port.
In a fluid or solids pumping system, it is potentially damaging to the system if a pumping source is dead-headed, that is, if the pumping source pumps into a blind conduit or if the inlet port to the pump is closed. This situation can arise, for example, if a valve within the system is adjusted incorrectly so that the fluid flow passage into or out of the pump is blocked.
Some valves have been developed to prevent a passage from being blocked, in an effort to prevent subsequent damage to the pump or other system components caused by a blocked passage. An example of such a valve is disclosed by Johnson in U.S. Pat. No. 4,470,429. Johnson discloses a three-way valve, having an inlet port and two exit ports. A fluid flowing into the valve can be directed to exit the valve through a selected one of the exit ports by blocking off the other exit port. This is achieved by rotating a flow plug inside the valve to block the other non-selected port. The flow plug is mounted on a shaft and an engageable stop is mounted on the closure lid of the valve. As the shaft is rotated, the stop on the closure lid engages a stop member on the shaft, preventing the flow plug from being rotated into a position wherein the inlet port is blocked.
A disadvantage with Johnson is that when the valve is disassembled for maintenance, a maintenance person can inadvertently reattach the lid in the wrong orientation so that the stop member on the lid is not positioned to prevent the flow plug from blocking the inlet port.
In accordance with a first preferred embodiment, the present invention is directed to a multi-port valve, comprising a housing, a flow plug and a stop. The housing defines a valve cavity and has at least three ports. The flow plug is moveably mounted within the valve cavity between a first position wherein the flow plug prevents flow through at least a portion of a first port and a second position wherein the flow plug prevents flow through at least a portion of a second port. The stop is associated with the housing to interact with the flow plug to prevent the flow plug from blocking flow through all of the third port.
In accordance with a second preferred embodiment, the present invention also is directed to a multi-port valve comprising a housing, a flow plug and a stop. The housing defines a valve cavity and has at least three ports. The flow plug is moveably mounted within the valve cavity between a first position wherein the flow plug prevents flow through at least a portion of a first port and a second position wherein the flow plug prevents flow through at least a portion of a second port. The stop is positioned proximate a third port and has at least a portion in the cavity to interact with the flow plug to prevent the plug from blocking the third port.
In accordance with a third preferred embodiment, the present invention also is directed to a method of preventing flow blockage of a selected port in a multi-port valve. The valve comprises a housing and a flow plug. The housing defines a valve cavity and has at least three ports. The flow plug is positionable within the valve cavity between a first position wherein the flow plug is adapted to prevent flow through a first port and a second position wherein the flow plug is adapted to prevent flow through a second port. The method comprises:
attaching a stop into a third port so that the stop extends into the cavity to contact the flow plug to prevent the flow plug from blocking flow through the third port; and
attaching a conduit to each of the ports.